The modules includes ultrasonic transmitters, receiver and control circuit. The basic principle of work is based on IO trigger for at least 10us high level signal. 
The Module automatically sends eight 40 kHz ultrasonic waves. After colliding with an object these waves return back and sensor detect received pulse signal. The duration of pulse from sending to receive back is used to calculate the distance of an object.

Features:

• Platforms: Arduino, Raspbery Pi, ESP8266
• Working Voltage: DC 5 V
• Working Current: 15mA
• Working Frequency: 40Hz
• Max Range: 4m
• Min Range: 2cm
• Measuring Angle: 15 degree
• Trigger Input Signal: 10uS TTL pulse

Datasheet:

Datasheet can be found here.